15kW Solar Battery Price in Ireland: What 15 and 20 kWh Really Cost in 2026

A 15 kWh battery installed alongside new solar panels in Ireland works out at roughly €6,000 to €9,500 in 2026, and 20 kWh at roughly €7,500 to €13,000. No Irish source publishes a price at these sizes, so those are built from published Irish per-kWh rates rather than quoted anywhere, and the ranges are wide because stacks at this size really do vary that much. Three things matter more than the headline number. SEAI's battery grant is a flat €600 from 5 kWh upwards, so it does not grow with the stack. The VAT treatment is worth two to five times the grant at these sizes. And a 4 kWp roof, the largest the solar grant will fund, produces about 4.4 kWh on a December day, which is barely a fifth of a 20 kWh battery.

What 15 and 20 kWh Cost, and How That Figure Is Built

Irish price guides stop at 10 kWh. Selectra's September 2026 battery guide tops out at a 10 kWh unit for €4,500 to €7,000 installed. Irish retailer Solarboss publishes battery-only pricing of €2,000 to €3,500 for 5 kWh and €3,000 to €5,000 for 8 kWh. SEAI's own figure for a battery fully installed is €3,500 to €5,500. Nobody prints a 15 or a 20.

So the figures below are assembled rather than quoted. The two published Irish step-ups, 5 kWh to 8 kWh at Solarboss and 5 kWh to 10 kWh at Selectra, imply a marginal rate of about €350 to €700 for each extra kWh of capacity. Apply that to the €4,000 to €6,000 installed price we have verified for 10 kWh and you get the planning ranges in the table. Treat them as a sanity check on quotes, not as a price list.

That the 13.5 kWh Powerwall sits inside the derived 15 kWh range is a useful cross-check: a premium single unit lands where a mainstream modular stack of similar size lands, which is roughly what you would expect.

Retrofitting to panels you already own costs more, as it does at every size. Our 5 kWh price guide documents a gap of around €1,000 between the day-one price and the retrofit price, and at 15 or 20 kWh the gap tends to be wider, because a stack this size is more likely to need a bigger hybrid inverter than the one already on your wall.

The Grant Does Not Get Bigger

SEAI's Battery Energy Storage System grant is a flat €600 for any battery of 5 kWh or larger. Batteries under 5 kWh are not eligible at all. There is no tier, no per-kWh rate and no upper band, so the same €600 arrives whether you install 5 kWh or 50. That makes the subsidy per unit of storage shrink as the stack grows:

The solar side is separate and unaffected by battery size. The SEAI Solar Electricity Grant pays €700 per kWp up to 2 kWp and €200 for each additional kWp up to 4 kWp, capped at €1,800. Add the battery grant and the maximum the State will put towards panels and storage together is €2,400. Full conditions are in our battery grant guide.

Three rules in the small print matter more at this size than at 5 or 10 kWh:

• One battery grant per MPRN, ever. The grant is not open to a home that has already had funding for a battery at that meter point. If you claim the €600 on a 10 kWh stack now and add modules in two years, there is no second €600.
• You must have the Grant Offer before anything is installed. SEAI will not accept an application for an installation that has already started, which rules out claiming after the fact on a stack you have been quietly expanding.
• The house must have been built and occupied before 2025, and the work must be done by an SEAI-registered solar PV contractor. A post-works BER is required where solar PV is present. You then have eight months from the offer to finish and submit the paperwork.

One case the published rules do not settle: a home with an existing battery that never received a grant, now adding modules to reach 15 or 20 kWh. There is no previous funding at that MPRN, so the eligibility bar appears to be clear, but SEAI's criteria do not say whether expanding an existing stack counts as installing a battery system. Put that question to SEAI at solarpv@seai.ie before you commit, not after.

The VAT Decision Is Worth More Than the Grant

SEAI states the position plainly: if you install the battery at the same time as solar panels there is 0% VAT on the battery, and if it is a standalone installation there is 23% VAT on top. Revenue's zero rate applies to the supply and installation of solar panels on private dwellings, and the battery rides along when it is part of the same supply-and-install contract.

At 5 kWh that is an interesting footnote. At 20 kWh it is the biggest single number in the decision:

So the VAT treatment on a 20 kWh stack is worth roughly three to five times the €600 grant everyone talks about. If you are going to buy a big battery and you are also going to put panels on the roof at some point, doing both under one contract is the single cheapest decision available to you. If the panels are already up, ask each installer in writing which rate they are applying and why, because the answer changes the price by more than the brand of battery does.

Can an Irish Roof Even Fill 20 kWh?

This is the question that should decide the size, and it is the one no quote answers. PVGIS modelling for a south-facing roof at 35 degrees in Dublin gives about 34 kWh per kWp installed in December, against about 124 kWh per kWp in May. For a 4 kWp array, the largest the solar grant will fund, that is:

• December: about 137 kWh for the whole month, or roughly 4.4 kWh a day. That is the total the panels make, before the house uses any of it.
• May: about 495 kWh for the month, or roughly 16 kWh a day gross.
• November to February together: about 17% of the year's output.

A typical Irish home uses about 4,200 kWh a year, the CRU reference figure, which is roughly 11.5 kWh a day, and a good share of that is drawn in daylight while the panels are working. To fill a 20 kWh battery from solar you need a day where generation exceeds household use by 20 kWh. On a 4 kWp roof that does not happen in Ireland outside a handful of the brightest days in May, June and July. In December the entire day's generation would not fill a quarter of it.

So What Does the Extra Capacity Earn?

Only one mechanism reliably fills the top half of a big stack: cheap overnight electricity. Electric Ireland's Night Boost band is around 10.88c per kWh between 2am and 4am and Energia's EV Smart Drive is around 9.42c from 2am to 6am, against roughly 29.81c on a standard 24-hour smart plan. Call the gross spread about 19c per kWh. Round-trip efficiency on a home battery runs about 85% to 95%, so the net value of each unit you shift is in the region of 16c to 18c.

Run that over the extra capacity, taking 17c as the mid-point:

Cycling every day is the ceiling, not the expectation. Through the summer the first 10 kWh fills itself off the roof for nothing and the extra capacity has nothing to do unless you pay to fill it, which defeats the purpose. The six-month column is the realistic case, and on that basis the increment pays back in roughly 11 to 23 years. The first 10 kWh, by comparison, pays back in about 6 to 10 years.

That matters because of what SEAI publishes about battery life: a typical 10-year warranty guaranteeing at least 70% of original capacity, and a cell rating of 6,000 to 10,000 cycles. Cycled hard, the hardware comfortably outlasts the warranty. Cycled gently, which is what a half-empty oversized stack means, a payback of 11 to 23 years on the extra capacity is a payback that runs past the warranty.

Two things improve the picture, and they are the reason to buy 15 or 20 kWh at all:

• A dynamic tariff. Since 1 June 2026, five major suppliers must offer at least one half-hourly dynamic tariff under the CRU mandate. Half-hourly pricing widens the spread beyond a fixed night band, and the wider the spread, the more a big battery is worth. The detail is in our dynamic tariffs guide, and the fixed-window alternative is in our night rate guide.
• Genuinely large consumption. Selectra's sizing table puts 10 to 15 kWh and up against homes using 15 to 25 kWh a day, which in practice means an EV, a heat pump, or both. A typical EV charge is 10 to 15 kWh on its own, so one car refilled from the battery uses capacity the average household never would. See charging an EV from solar for how that interacts with export payments.

If you are storing rather than exporting, the comparison that decides each unit is the gap between your import rate and your export rate. Electric Ireland currently pays 19.5c per kWh under the Clean Export Guarantee, and SEAI puts the typical export payment at 18 to 20c against roughly 35c to buy a unit back. Storing a solar unit instead of selling it is worth the difference, which is a far better trade than buying overnight units, and the reason the first 10 kWh always pays better than the last.

Two Practical Constraints at This Size

Your inverter and your grid connection. Most Irish homes connect micro-generation on an NC6 notification, which covers up to 6 kW single phase or 11 kW three phase. A big stack often arrives with a bigger hybrid inverter, and if the quote specifies one rated above 6 kW on a single-phase supply, you are no longer making a notification: it becomes an NC7 connection application, which is a slower and more involved process. Ask which form the installer is filing before you sign. Either way, ESB Networks needs the application before the battery goes in, and SEAI says to allow at least four weeks, or 20 working days.

Where it physically goes. SEAI puts a typical battery at about 100cm high, 60cm wide and 25cm deep, and notes the height increases as you add modules to a modular system. A 15 or 20 kWh stack is therefore taller than the single unit in the brochure photograph. SEAI recommends installing outside or in an outbuilding in a suitable enclosure, and if it has to go indoors, in a well-ventilated space with fresh-air ventilation. It also advises checking with your home insurer before an indoor installation, which is worth doing in writing at this size: see our guide to solar panels and home insurance.

SEAI's own advice is to consider a modular battery so capacity can be added later rather than replacing the whole unit. That is sound, with one wrinkle this page has already covered: the grant is once per MPRN, so starting at 10 kWh and expanding later gets you the €600 once, on the first install.

15 or 20 kWh: Who Should Buy Which

• Stay at 10 kWh if your array is 4 kWp or smaller, you are on a flat tariff, and you have no EV. The capacity above 10 kWh will spend most of the year empty, and empty capacity earns nothing. Our 10 kWh guide has the per-kWh case.
• 15 kWh suits a high-consumption house with either an EV or a heat pump, on a night rate or a dynamic tariff, with a 5 kWp array or larger. It is the size that still cycles most days in winter.
• 20 kWh earns its keep in a house with an EV and electric heating, on a dynamic tariff, with somebody at home during the day. Without the tariff it is hard to justify: you are buying storage that the roof cannot fill and the tariff will not reward.
• If backup through a power cut is the real motive, size on the hours you want to cover rather than on savings, and read our guide to solar panels in a power cut first. A standard installation disconnects during an outage. Keeping the lights on needs a changeover switch specified at quote stage.

Whether a battery is worth it at all, before size enters the conversation, is covered in solar panels with a battery: worth it? and the wider battery storage guide.

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